Patent GB-1286153-A (GB)
Title: Charge/discharge arrangements for nuclear reactors
Inventor: PUGH JOHN
IPC: G21C19/16
Filed: 1969-04-03
Abstract: 1286153 Fuelling reactors UNITED KING- DOM ATOMIC ENERGY AUTHORITY 18 March 1970 [3 April 1969] 17734/69 Heading G6C A gas-cooled reactor has a core 2 formed by columns of fuel-bearing moderator blocks 5 of pentagonal shape, Figs. 1, 2, each having a central hole 6. To facilitate removal of the blocks for refuelling, clearances are provided between their adjacent faces but in normal operation of the reactor the effect of these clearances is nullified by spreader rods 74 inserted in holes 7a formed by arcuate surfaces on the block exteriors. The holes 7a are on a square lattice as are also holes 7b for control rods. The columns of blocks 5 are arranged in groups of four about the axis of a hole 7a and a standpipe 8a is provided in alignment with each hole 7a, the standpipes extending through the top cap la of a concrete pressure vessel 1. A mobile refuelling machine 9 is connected to a selected standpipe 8a when refuelling is required. The refuelling machine 9 comprises, Fig. 3, a compartment 9a having upper and lower extensions 9b, 9c housing a guide tube 10 for the fuel block handling assembly 24, 25, the tube being supported by a winch whereby it may be lowered through the standpipe 8a to the position shown after the removal of shield plugs (not shown). Exact alignment of the guide tube 10 with a hole 7a is performed by simultaneous adjustment of funnels 11, 12 which are penetrated by the tube. The funnels eccentrically-mounted on respective ring-gears 18, 19 driven by a shaft 22 through pinions 21, 20 for providing fine adjustment. To provide for coarse adjustment the ring-gears 18, 19 are rotatably mounted on arms 13 carried by a shaft 14, toothed racks 15 on the shaft 14 being driven by a shaft 17 through pinions 16. Thus misalignment between the standpipe 8a and hole 7a  due to thermal distortion may be compensated for a drive cylinder 24 is slidably suspended within the tube 10 by cables (Fig. 4, not shown) and carries a winch for supporting a charging column 25 by means of cables C. Motors (not shown) within the cylinder 24 respectively drive shafts 26, 29 for rotating gearing within the column 25. To permit relative vertical movement between the components 24, 25, the shafts 26, 29 are slidable with respect to the gears they drive in the column 25. A drum 50 rotatable about an axis YY on bearings 51 within the column 25 supports a tube 32 rotatable about an eccentric axis ZZ on bearings 31. The lower end of the tube 32 has a cranked portion 32a carrying a depending tube portion 32b provided with gripper latches 37. In operation, the column 25 is first lowered relatively to the cylinder 24 to remove the spreader plug 74 in hole 7a by means of the latches 37 and secondly to allow the tube portion 32b to enter the hole 6 of the selected block 5 and lift the block by the latches. The tube portion 32b is brought into the required alignment by rotating shaft 29 which causes, through gearing, simultaneous rotation of the drum 50 about axis YY and tube 32 about axis ZZ, the gearing ratio being such that when the drum rotates through 128¢ degrees the tube rotates through 180 degrees. After the initial lifting of the block above the core level it is moved laterally by rotation of the shaft 29 so that it is aligned with the axis of the tube 10, i.e., axis YY. Finally, the components 24, 25 are raised together into the upper extension 9b of the machine 9 and the block 5 is released. Actuation of the gripper latches 37 is performed by rotation of the shaft 26 to cause, through gearing, rotation of a tube 33a within the tube 32, this tube having a screw-threaded connection 34 with a rod 33b whereby the latter is moved longitudinally. The rod 33b has a cranked extension 35 within the cranked tube portion 32a and a depending portion 36 within the tube portion 32b which co-operates with the latches 37.